1/* Measure nanosleep timer latency
2 *              by: john stultz (john.stultz@linaro.org)
3 *		(C) Copyright Linaro 2013
4 *              Licensed under the GPLv2
5 *
6 *  To build:
7 *	$ gcc nsleep-lat.c -o nsleep-lat -lrt
8 *
9 *   This program is free software: you can redistribute it and/or modify
10 *   it under the terms of the GNU General Public License as published by
11 *   the Free Software Foundation, either version 2 of the License, or
12 *   (at your option) any later version.
13 *
14 *   This program is distributed in the hope that it will be useful,
15 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
16 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17 *   GNU General Public License for more details.
18 */
19
20#include <stdio.h>
21#include <stdlib.h>
22#include <time.h>
23#include <sys/time.h>
24#include <sys/timex.h>
25#include <string.h>
26#include <signal.h>
27#include "../kselftest.h"
28
29#define NSEC_PER_SEC 1000000000ULL
30
31#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
32
33
34#define CLOCK_REALTIME			0
35#define CLOCK_MONOTONIC			1
36#define CLOCK_PROCESS_CPUTIME_ID	2
37#define CLOCK_THREAD_CPUTIME_ID		3
38#define CLOCK_MONOTONIC_RAW		4
39#define CLOCK_REALTIME_COARSE		5
40#define CLOCK_MONOTONIC_COARSE		6
41#define CLOCK_BOOTTIME			7
42#define CLOCK_REALTIME_ALARM		8
43#define CLOCK_BOOTTIME_ALARM		9
44#define CLOCK_HWSPECIFIC		10
45#define CLOCK_TAI			11
46#define NR_CLOCKIDS			12
47
48#define UNSUPPORTED 0xf00f
49
50char *clockstring(int clockid)
51{
52	switch (clockid) {
53	case CLOCK_REALTIME:
54		return "CLOCK_REALTIME";
55	case CLOCK_MONOTONIC:
56		return "CLOCK_MONOTONIC";
57	case CLOCK_PROCESS_CPUTIME_ID:
58		return "CLOCK_PROCESS_CPUTIME_ID";
59	case CLOCK_THREAD_CPUTIME_ID:
60		return "CLOCK_THREAD_CPUTIME_ID";
61	case CLOCK_MONOTONIC_RAW:
62		return "CLOCK_MONOTONIC_RAW";
63	case CLOCK_REALTIME_COARSE:
64		return "CLOCK_REALTIME_COARSE";
65	case CLOCK_MONOTONIC_COARSE:
66		return "CLOCK_MONOTONIC_COARSE";
67	case CLOCK_BOOTTIME:
68		return "CLOCK_BOOTTIME";
69	case CLOCK_REALTIME_ALARM:
70		return "CLOCK_REALTIME_ALARM";
71	case CLOCK_BOOTTIME_ALARM:
72		return "CLOCK_BOOTTIME_ALARM";
73	case CLOCK_TAI:
74		return "CLOCK_TAI";
75	};
76	return "UNKNOWN_CLOCKID";
77}
78
79struct timespec timespec_add(struct timespec ts, unsigned long long ns)
80{
81	ts.tv_nsec += ns;
82	while (ts.tv_nsec >= NSEC_PER_SEC) {
83		ts.tv_nsec -= NSEC_PER_SEC;
84		ts.tv_sec++;
85	}
86	return ts;
87}
88
89
90long long timespec_sub(struct timespec a, struct timespec b)
91{
92	long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
93
94	ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
95	return ret;
96}
97
98int nanosleep_lat_test(int clockid, long long ns)
99{
100	struct timespec start, end, target;
101	long long latency = 0;
102	int i, count;
103
104	target.tv_sec = ns/NSEC_PER_SEC;
105	target.tv_nsec = ns%NSEC_PER_SEC;
106
107	if (clock_gettime(clockid, &start))
108		return UNSUPPORTED;
109	if (clock_nanosleep(clockid, 0, &target, NULL))
110		return UNSUPPORTED;
111
112	count = 10;
113
114	/* First check relative latency */
115	clock_gettime(clockid, &start);
116	for (i = 0; i < count; i++)
117		clock_nanosleep(clockid, 0, &target, NULL);
118	clock_gettime(clockid, &end);
119
120	if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
121		ksft_print_msg("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
122		return -1;
123	}
124
125	/* Next check absolute latency */
126	for (i = 0; i < count; i++) {
127		clock_gettime(clockid, &start);
128		target = timespec_add(start, ns);
129		clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
130		clock_gettime(clockid, &end);
131		latency += timespec_sub(target, end);
132	}
133
134	if (latency/count > UNRESONABLE_LATENCY) {
135		ksft_print_msg("Large abs latency: %lld ns :", latency/count);
136		return -1;
137	}
138
139	return 0;
140}
141
142#define SKIPPED_CLOCK_COUNT 3
143
144int main(int argc, char **argv)
145{
146	long long length;
147	int clockid, ret;
148
149	ksft_print_header();
150	ksft_set_plan(NR_CLOCKIDS - CLOCK_REALTIME - SKIPPED_CLOCK_COUNT);
151
152	for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
153
154		/* Skip cputime clockids since nanosleep won't increment cputime */
155		if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
156				clockid == CLOCK_THREAD_CPUTIME_ID ||
157				clockid == CLOCK_HWSPECIFIC)
158			continue;
159
160		length = 10;
161		while (length <= (NSEC_PER_SEC * 10)) {
162			ret = nanosleep_lat_test(clockid, length);
163			if (ret)
164				break;
165			length *= 100;
166
167		}
168
169		if (ret == UNSUPPORTED) {
170			ksft_test_result_skip("%s\n", clockstring(clockid));
171		} else {
172			ksft_test_result(ret >= 0, "%s\n",
173					 clockstring(clockid));
174		}
175	}
176
177	ksft_finished();
178}
179